The present invention relates to a digital audio tape record/play-back system for recording/playing back character data together with digital audio data.
The recent developments of audio equipment are remarkable. A typical example is a compact disk player for playing back data on a disk on which an audio signal is digitized and recorded.
In the field of tape recorders, studies on a digital tape recorder (DAT) system (disclosed in, e.g U.S. Pat. No. 4,523,237 to S. FUKUDA et al.) for recording/playing data on/from a magnetic tape have been made.
According to the DAT system, an analog audio signal is recorded in the form of a PCM signal on a DAT tape. The PCM signal is played back in the form of an analog audio signal. The DAT system can record and play back PCM signals with higher fidelity than a conventional analog recording system.
In order to best understand the present invention, general DAT standards will be described below.
A DAT (digital audio tape recorder) conference was established in 1981 to achieve DAT design standardization. DATs are classified into a stationary head type DAT (S-DAT) and a rotary head type DAT (R-DAT). The R-DAT is considerately used as commercial equipment since it can employ known 1/2-inch VTR techniques. Both the S- and R-DATs have a 48-kHz sampling frequency and 16-bit quantization. A DAT tape has a width of 3.81 mm, and a tape cassette for R-DAT is 73.times.54.times.10.5 mm.sup.3. An R-DAT head drum has a diameter of 30 mm, a speed of 2,000 rpm, and a tape winding angle of 90 degrees. One track (one record of one head, a 23.501-mm tape portion of 7.5-ms period) is divided into 196 blocks. PCM data including parity data constitutes 128 blocks. One block consists of 288 bits.
When a standard tape cassette is used the R-DAT can perform 2-hour continuous record/play-back operation. Therefore, when a plurality of musical pieces (one musical piece has a length of about 3 minutes) are recorded using this R-DAT, a very large number of musical pieces (i.e., 40) can be recorded. It is very difficult to search a musical piece to be played back from the tape recording such a large number of musical pieces. For this reason, in the DAT standards, a program number can be recorded for each musical piece (program), and a desired program number can be input to easily search the corresponding musical piece. However, in the method using the program number, a user must know a correspondence between musical pieces recorded on the tape and program numbers. For this purpose, program numbers and titles of musical pieces are written on a label of a tape cassette. Thus, a user finds a program number corresponding to a desired musical piece in accordance with the content of this label and can input the program number. However, if a user loses this label, he can hardly know a correspondence between program numbers and titles.
A compact cassette recorder which is spread worldwide also has the above-mentioned drawbacks, and studies for eliminating the drawbacks have been made. For example, as shown in U.S. Pat. No. 4,615,024 to M. Usui, a title is recorded on a starting portion of a recording area for each musical piece, and the title is input to search the corresponding musical piece. As is known, in a compact cassette tape, signals are recorded parallel to the longitudinal direction of the tape. In the above method, a title recording area is followed by a musical piece recording area.
However, this technique cannot be applied to the R-DAT without modification. This is because in the R-DAT, signals are recorded not parallel to the longitudinal direction of the tape like in the compact cassette tape recorder but are recorded as discontinuous tracks which are inclined at about 6 degrees with respect to the longitudinal direction of the tape. More specifically, when recorded title data is read while traveling a tape at a speed 100 to 200 times a normal play-back speed, a rotary head is traced over a plurality of tracks. For this reason, the rotary head may fail to trace the title recording area. Therefore, a desired musical piece may not often be searched.
Thus, a demand has arisen for development of a recording method of titles (not limited to a title of a musical piece but can be characters) complying with the R-DAT standards.